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Micro Exam 2 > Ebright: Infectious Diseases of the GI Tract > Flashcards

Ebright: Infectious Diseases of the GI Tract Flashcards

1
Q

Mild diarrhea definition:

A

Production of up to 3 loose stools per day without abdominal or systemic symptoms.

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2
Q

Moderate to severe diarrhea definition:
Local symptoms:
Systemic symptoms:

A

4 or more loose stools per day, often associated with other symptoms

Local symptoms: abdominal cramps, N/V, or tenesmus (painful defecation)

Systemic symptoms: fever, malaise, or dehydration

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3
Q

Diarrhea worldwide:

A

Second leading cause of death behind acute respiratory infections

Major death toll in children

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4
Q

What bacteria cause GI disease? (9)

A 
Shigella
Salmonella
E.coli
Campylobacter
Yersinia
Vibrio cholera
Clostridium difficile
Aeromonas hydrophila
Bacillus cereus
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5
Q

What protozoa cause GI disease? (6)

A 
Giardia lamblia
Cryptosporidia
Entameoba histolytica
Isospora belli
Cyclospora
Microsporidia
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6
Q

What viruses cause GI disease? (4)

A

Rotavirus
Adenovirus (serotypes 40 and 41)
Calcivirus (Norovirus)
Astrovirus

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7
Q

What fungus causes GI disease? (1)

A

Candida (?)

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8
Q

What is the mechanism of disease production for the majority of diarrhea?

A

Non-Inflammatory

Basics: majority of diarrhea; usually involves small intestine

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9
Q

Non-Inflammatory

Diarrhea may result from overproduction of enterotoxin from what organisms (4):

A

Vibrio cholera

ETEC

Bacillus cereus

Clostrium perfrigens

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10
Q

Non-Inflammatory

Diarrhea may result from other processes that alter absorptive function of villus tip due to what organisms (5):

A 
EPEC
Cryptosporidium
Giardia
Rotavirus
Norovirus
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11
Q

Inflammatory

Basics:

A

Often involves invasion of GI mucosa and/or production of cytotoxin; usually involves the colon

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12
Q

Inflammatory

Examples:

A 
Shigella
Salmonella
Campylobacter
Clostridium difficile (cytotoxn)
Entamoeba histolytica
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13
Q

What causes Bacteremia and Systemic Infection? (3)

A

Enteric fever (typhoid)

Non-typhoid salmonella bacteremia

Shigella, campylobacter and listeria can all cause bacteremia (less common)

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14
Q

Classification of GI disease by Clinical Presentation

Emphasis on N/V rather than diarrhea; absent or low grade fever; upper abdominal symptoms (3)

A

Staphylococcus aureus (preformed enterotoxin in food)

Bacillus cereus (emetic form; preformed enterotoxin in food)

Heavy metal food poisoning

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15
Q

Classification of GI disease by Clinical Presentation

Emphasis of N/V and large volume diarrhea (watery); absent or low grade fever); small intestine disease (8)

A 
o	Vibrio cholera
o	ETEC
o	Bacillus cereus (diarrheal form)
o	Clostridium perfringens
o	Giardia lamblia
o	Rotavirus
o	Norovirus
o	Cryptosporidium
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16
Q

Classification of GI disease by Clinical Presentation

Emphasis on lower intestinal (colon) symptoms; smaller volume frequent stools with blood and leukocytes; tenesmus, fever, abdominal cramps (6)

A 
o	Shigella
o	Salmonella (colonic form)
o	Campylobacter
o	Non-cholera vibrios (ie. V.parahemolyticus)
o	EIEC
o	Entamoeba histolytica
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17
Q

Classification of GI disease by Clinical Presentation

Emphasis on systemic illness with toxicity, prostration, high fever; diarrhea may be absent (2)

A

o Enteric fever (Samonella typhi)

o Non-typhoid salmonella bacteremias

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18
Q

By Social Setting/Underlying Immune Status of Host

Hospital Acquired (Nosocomial): (2)

A 
o	Clostridium difficile
o	Rotavirus (especially in young children)
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19
Q

By Social Setting/Underlying Immune Status of Host

Day Care: (4)

A

o Shigella
o Rotavirus
o Giardia
o Cryptosporidium

.

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20
Q

By Social Setting/Underlying Immune Status of Host

Traveler’s Diarrhea: (4)

A

o ETEC
o Giardia
o Salmonella
o Shigella

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21
Q

By Social Setting/Underlying Immune Status of Host

Food Borne: (6)

A 
o	Norovirus (majority) 
o	Other bacterial causes include Salmonella, Campylobacter, E.coli, Clostridium perfringens, and Shigella
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22
Q

By Social Setting/Underlying Immune Status of Host

Water Borne: (6)

A 
o	Giardia
o	Cryptosporidium
o	E.coli
o	Salmonella
o	Campylobacter
o	Norovirus
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23
Q

By Social Setting/Underlying Immune Status of Host

Patients with AIDS: (5
Natalja’s)

A

Increased risk for any type of infection

Special risks also associated with AIDS patients who are immunocompromised: Mycobacterium avium, Cryptosporidium, Cyclospora, Giardia, Microsporidia

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24
Q

Enteropathogenic E.coli (EPEC)

Common Presentation:
Pathogenesis:
Diagnosis:

A

Common Presentation: epidemic infantile diarrhea (ie. hospital nursery outbreaks), especially in developing countries

Pathogenesis: adhere to and efface the brush border of the small intestine

Diagnosis: not available in a routine lab

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25
Q

Enterohemorrhagic E.coli (EHEC)

Most common cause:
Produces:
Pathogenesis is similar to:

A

Cause: most commonly O157:H7 serotype that produces Shiga toxin (not the only one that produces this); often associated with undercooked ground beef

Pathogenesis: similar to EPEC, but with the presence of Shiga toxin (toxic to epithelial and endothelial cells)

26
Q

Enterohemorrhagic E.coli (EHEC)

Presentation:
Diagnosis:
What do antibiotics cause?

A

Presentation: severe abdominal cramps, bloody diarrhea; may or may not have fever and fecal leukocytes

Diagnosis: SMAC growth will be sorbitol negative

Antibiotics are NOT effective: can also promote hemolytic uremic syndrome

27
Q

What is the most common cause of acute bacterial diarrhea worldwide (especially traveler’s and children under 2)

A

Enterotoxigenic E.coli (ETEC)

28
Q

Enterotoxigenic E.coli (ETEC)

Transmission:
Toxins:
What is similar to cholera? What does it result in?

A

Transmission: most commonly via contaminated food

Toxins: plasmid mediated enterotoxin (heat labile and heat stable)
- Heat Labile: similar to cholera (activates adenylate cyclase to increase cAMP); results in chloride and water secretion

29
Q

Enterotoxigenic E.coli (ETEC)

Presentation:
Diagnosis:
Treatment:

A

Presentation: large volume watery diarrhea

Diagnosis: not available in routine lab

Treatment: trimethoprim-sulfa or ciprofloxacin

30
Q

Enteroinvasive E.coli (EIEC)

Presentation:
Similar to:
Diagnosis:

A

Presentation: uncommon outbreaks of dysentery in adults, often transmitted by food

Similar to Shigella: invasiveness

Diagnosis: not available in routine lab

31
Q

Enteroaggregative E.coli (EAEC)

“Stacked brick” adherence to:
Recently identified as a cause for: (3)

A

“Stacked brick” adherence to Hep-2 cells

Recently identified as a cause for:
o Traveler’s diarrhea
o Persistent childhood diarrhea in developing countries
o Chronic diarrhea in AIDS patients

32
Q

Salmonella
Taxonomy

Most common types in the US:
What type frequently causes bacteremia?

A

S.enteritidis and S.typimurium: most common in US

S.choleraesuis: frequently causes bacteremia

33
Q

Salmonella
Taxonomy

What type is widely distributed in animal kingdom?
What has only humans as hosts?

A

Non-typhi Salmonella: widely distributed in animal kingdom

S.typhi and S.paratyphi: only human hosts

34
Q

Salmonella

Transmission:
Diagnosis:

A

Transmission: Via contaminated food and water

Diagnosis: culture of stool or blood

35
Q

Salmonella

Clinical Presentations (3):

A

Gastroenteritis

Enteric fever (typhoid)

Extra-intestinal infection

36
Q

Salmonella

Treatment:
In the case of gastroenteritis:

A

Antibiotics for enteric fever and extra-intestinal infections (not usually given for gastroenteritis unless it is an extreme case- age, immunocompromised, AIDS, sickle cell)

37
Q

Shigella

Types: (4)

A

Taxonomy: S.dysenteriae, boydii, flexneri and sonnei

38
Q

Shigella

Most common type in the US:
AIDS patients:

A

S.sonnei: most common in the US

S.flexneri: most common in AIDS patients

39
Q

Shigella

What does type 1 S.dysenteriae produce?
S.dysenteriae complications: (5)

A

S.dysenteriae: type 1 produces Shiga toxin (cytotoxin)

Complications: hemolytic uremic syndrome (HUS), toxic megacolon, encephalopathy, seizures, reactive arthritis

40
Q

Shigella

Diagnosis:
Treatment:

A

Diagnosis: by stool culture (bacteremia is rare therefore blood cultures will be negative)

Treatment: antibiotics given in moderate to severe illness (shortens course and reduces transmission)

41
Q

Cholera

Epidemic cholera is caused by what types?
Transmission:
Disease is mediated by:

A

Epidemic cholera: Vibrio cholera 01 and 0139

Transmission: contaminated water or food, or poorly cooked shellfish

Disease: Classic non-inflammatory diarrhea mediated by enterotoxin (choleragen)

42
Q

Cholera

Pathogenesis:
Diagnosis:
Treatment:

A

Pathogenesis: patients due from dehydration and electrolyte loss

Diagnosis: can be made in most labs by stool culture HOWEVER, most labs in the US don’t test for it (because it is uncommon) unless instructed to

Treatment: aggressive rehydration and antibiotics to shorten the illness (tetracycline or azithromycin)

43
Q

What is the most frequent cause of bacterial enteritis in developed countries?

A

Campylobacter

44
Q

Campylobacter

Transmission:
Symptoms:

A

Transmission: often from handling and consuming poultry

Symptoms: diarrhea and severe cramping abdominal pain

45
Q

Campylobacter

What is a possible sequelae post-infection?

A

Guillan Barre Syndrome

46
Q

Campylobacter

Diagnosis:
Treatment:

A

Diagnosis: can be made in most labs using microaerophilic atmosphere and 42 degrees C

Treatment: erythromycin given to those with marked symptoms or immunocompromised; resistance to quinolones is increasing

47
Q

Clostridium difficile

Common cause of what?
Symptoms:
What can colitis form?

A

Common cause of hospital-acquired diarrhea: due to preceding antibiotic use (predisposes colon to overgrowth)

Symptoms: inflammatory colitis and diarrhea
- Colitis can be severe: with formation of pseudomembranes

48
Q

Clostridium difficile

Diagnosis:
Treatment:

A

Diagnosis: tissue-culture assay or EIA/PCR on stool sample

Treatment: oral metronidazole or vancomycin

49
Q

What is the most common cause of acute gastroenteritis and food poisoning in the US?

A

Norovirus

50
Q

Norovirus

Symptoms:
Diagnosis:
Treatment:

A

Symptoms: illness usually lasts 1-2 days with N/V/D

Diagnosis: using immune electron microscopy, RT-PCR (only available in reference labs such as CDC and state health departments)

No specific treatment

51
Q

What is the most common cause of severe diarrhea in children?

A

Rotavirus

  • Both in developed and developing countries
52
Q

Rotavirus

Common age groups:
Adults:
Genome type:

A

Common age groups: 6-24 months
Adults: have symptoms less often

dsRNA

53
Q

Rotavirus

Symptoms:
Seasonal:
Transmission:

A

Symptoms: N/V/D lasting 4-8 days

Seasonal: most common during the winter (sporadic rather than epidemic)

Transmission: fecal-oral (person to person)

54
Q

Rotavirus

Diagnosis:
Vaccine:
Treatment:

A

Diagnosis: analyze stool sample via immune electron microscopy or ELISA (can be done in most labs)

Vaccines: 2 new live, oral vaccines given during childhood

No specific treatment

55
Q

What is the most commonly reported parasitic disease in the US?

A

Giardia lambia

56
Q

Giardia lambia

Transmission:
Where does it inhabit?

A

Transmission: fecal-oral and contaminated food or water

Pathogenesis: inhabits upper small bowel, but does not invade the mucosa

57
Q

Giardia lambia

Lasts how long?
Symptoms:
Diagnosis:

A

Symptoms: usually last 5-7 days (after a 1-3 week incubation period); also often causes prolonged illness and diarrhea

Diagnosis: stool exam for cysts, small bowel biopsy, string test, or ELISA test to detect stool antigen

58
Q

Giardia lambia

Treatment: (3)

A

Treatment: metronidazole, furazolidone, or quinacrine

59
Q

RECOMMENDATIONS FOR COST-EFFECTIVE TESTING FOR ENTERIC PATHOGENS:

Routine Cultures should always include: (3)
Use up to 2 stool samples for what?

A

Routine Cultures should always include:
- Campylobacter, Salmonella, Shigella
- Other agents based on in-house or regional survey data
• Submit additional samples for less common bacteriologic agents: second-line test after common agents have been ruled out

Up to 2 stool samples for ova and parasite examination: can forego this testing with the emergence of specific tests for Giardia, Entamoeba histolytica and Cryptosporidium if these are the more likely causative agents

60
Q

RECOMMENDATIONS FOR COST-EFFECTIVE TESTING FOR ENTERIC PATHOGENS:

How many stool samples to rule out C.difficle?

Use 3-day rule for what?

A

2-3 samples to rule out Clostridium difficile: samples should be spaced several days apart

Use 3-day rule for all stool and parasite testing (in general, do not order after 3rd day of hospitalization)

Micro Exam 2 (18 decks)

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